A Light Emitting Diode (LED) is a display and lighting technology which is widely used in electrical and electronic products on the market as LEDs use less power, have longer lifetimes and produce little heat as compared to traditional incandescent light bulbs, as well as emit colored light. After assembly of an LED, each LED is tested to determine its optical and electrical properties before being sorted according to its determined characteristics. Since the characteristics of the assembled LEDs vary widely, an elaborate sorting system is used to classify and separate them after assembly.
In a conventional sorting system for LEDs, the LEDs are loaded onto a test handler. Characterization of LEDs is carried out by conducting tests such as optical and electrical tests. After testing, the LEDs are sorted in an offloader which has bins arranged in a matrix form. Each bin is assigned to receive LEDs having certain predetermined characteristic(s). An output tube channels each LED which is to be transferred into an allocated bin. Typically, the LED passes through an output confirmation sensor before being unloaded into the bin to ensure that the LED has successfully passed through the output tube. The next LED would only be unloaded into the output tube to an allocated bin after the output confirmation sensor has determined that the preceding LED has been successfully transferred.
It has been noted that while over a hundred bins may be deployed for collecting a batch of LEDs that are being sorted, some bins are typically utilised more often than others. This is due to the fact that some LEDs have characteristics which are more commonly exhibited than others. Hence, the bins corresponding to these LEDs are more frequently accessed by the output tube. In this regard, it would be useful for the bins to be classified according to more frequently used bins and less frequently used bins so that the output tube may be more efficiently utilized.
FIG. 1 is a schematic top view of a normal bin tray 14 in a conventional sorting system with a high speed bin tray 12 according to the preferred embodiment of the invention superimposed over it. Referring to the conventional sorting system comprising the normal bin tray 14, it would take a longer time for an output tube to move from bin a to bin b than for the output tube to move from bin a to bin c, which is of a shorter distance. Furthermore, if consecutive binning is necessary to alternately transfer LEDs to bin b and bin d, there is substantial motion time incurred for the output tube to repeatedly move between bins b and d. It would therefore be advantageous to place bins which are used more frequently in close proximity to one another in order to minimise the motion distance and time of the output tube. By reducing the motion distance of the output tube from one bin to another, the speed of sorting and the throughput of the LEDs may be increased. Moreover, by concentrating the frequently-used bins at one location, more compact and faster positioning mechanisms may be adopted for output devices used for these bins.
Additionally, in a conventional sorting system, each bin is preset to collect a certain number of LEDs. Once a preset counter determines that a maximum number of LEDs in a bin has been reached, it is necessary to set the conventional LED sorting machine to idle to allow the removal of the bin. Thus, the resultant down-time reduces the LED sorting speed and throughput. It would therefore be desirable for sorting operations to be allowed to continue while an operator removes some of the bins which are full.